Former Celtics captain Rajon Rondo has taken it upon himself to plan a players-only 10th anniversary celebration of the team’s NBA championship win at an undisclosed international location this coming summer, and everybody’s invited — except Ray Allen, according to The Undefeated’s Marc J. Spears.

When Allen turned down a more lucrative offer from the Celtics to sign with the rival Miami Heat a few months after LeBron James & Co. had come back to eliminate them in Game 7 of the 2012 Eastern Conference finals, Kevin Garnett announced on media day, “I don’t have Ray’s number anymore.”

“It will be a long story about that, but it is what it is,” Rondo, now a member of the Chicago Bulls, told Spears. “I don’t know a good analogy to put this in. It just wasn’t the greatest separation. It wasn’t the greatest thing that could’ve happened to us as a team, a bond. We were at war with those guys [Miami]. To go with the enemy, that’s unheard-of in sports. Well, it’s not so unheard of. It’s damn near common now.

“The mindset we had. The guys on our team. You wouldn’t do anything like that. It makes you question that series in the Finals. … Who were you for? You didn’t bleed green. People think we had a messed-up relationship. It’s not the greatest. But it’s not just me. I called and reached out to a couple of other vets and asked them what they wanted to do with the situation. They told me to stick with what we got [without Allen].”

Rondo has contacted every other member of the ’08 title team save for P.J. Brown, who he’s still trying to locate, and several members of the squad told him not to invite Allen, Spears reported.

“I mean, Ray left,” an anonymous teammate told The Undefeated. “He left to the enemy.”

At least one member of the team would prefer to see Allen invited. “I assumed that Ray would be invited,” Leon Powe, who now serves as a community ambassador in the Celtics organization, told Spears. “That is one of my guys. My preference is that Ray is extended an invitation.” Rondo claimed he would have invited Allen had enough players he polled not preferred to leave him off the list.

When Allen turned down a two-year, $12 million offer from the Celtics to sign a three-year, $9.5 million deal with the Heat in free agency, ex-Boston coach Doc Rivers admitted to The Vertical’s Adrian Wojnarowski at the time, “I was pissed at him. I was pissed at him for his reasons for leaving.”

Those reasons, Doc said, were the coach’s decisions to run the offense through Rondo and bench Allen in favor of Avery Bradley midway through 2011-12 — a move that coincided with a late-season turnaround that ended in the conference finals after Bradley had suffered a severe shoulder injury.

“For a week or two, I was really disappointed, pissed, because I thought it was for all the wrong reasons,” added Rivers, now coaching Pierce on the L.A. Clippers. “It was more about himself, his team. And then I realized: Well, it should be about himself. It was free agency. I wasn’t thinking right.”

Rivers preached “Ubuntu,” a South African concept adopted by Nelson Mandela, advocating togetherness. Allen’s departure was the first real disruption of the team’s core. Since then, the Celtics have traded all four of the 2008 team’s other starters — Rondo, Pierce, Garnett and Kendrick Perkins.

More recently, though, Pierce conceded to The Undefeated that Allen’s decision to join the rival Heat, coupled with the fact he didn’t discuss that decision with his Celtics teammates, led to Pierce’s frustration.

“That was a tough situation because we thought it was betrayal,” Pierce told Spears upon Allen’s official retirement. “That’s why the whole thing evolved like it did with us not talking to him. Ray didn’t really have the best relationship with Rondo anyway. That was nothing. [Rondo], me and Kevin, he didn’t have any talk with us [before his Miami decision].

“I tried to call him and I didn’t get any return calls before he signed with Miami. That was our rival. We were brothers. We came in together. We just wanted a heads-up or a ‘what’s on your mind?’ or something like. Then, all of a sudden, he left. That was the biggest disappointment on my end. Not even getting a callback at that moment.”

Pierce plans to join Garnett and Allen in retirement this summer, leaving Rondo and Tony Allen as the last remaining active players from the 2008 C’s. After KG and Allen arrived in Boston via trades in the summer of 2007, that group played in three conference finals and two NBA Finals, winning one title in their five years together, and may have won multiple rings if not for injuries over the last four years.

Allen also won a title in his first year as a member of the Heat, making one of the most famous shots in NBA history — a series-saving 3-pointer — in the process. He remains the NBA’s career leader in 3-point field goals, until Stephen Curry catches him one day, and it’s a shame his relationship with the Celtics has frayed so much. Pierce indicated earlier this season that they’re still not in communication.

When Allen officially announced his retirement this past November in a letter to his younger self for The Players’ Tribune, he discussed the military childhood, obsessively compulsive work ethic, private personality and other quirks that made it so difficult for him to fit in to locker rooms.

“But if I’m being real with you,” he wrote, “what you’ll realize after you win the first title is that the thrill is fleeting. The vindication is fleeting. If you only chase that high, you’re going to end up very depressed.”

He went to Miami because he thought it was best for him and his family. And, yeah, maybe he didn’t like Rondo all that much. In The Players’ Tribune piece, he credited Garnett, Pierce, James and Dwyane Wade for their leadership on their way to rings. Rondo was conveniently left out of the conversation.

The Celtics issued a statement thanking Allen for his service after news of his retirement, but Boston president of basketball operations Danny Ainge has indicated that — while Pierce and Garnett can expect to have their numbers retired in the Garden — Allen’s departure to Miami will obviously play “somewhat of a factor” in the team’s decision to raise his No. 20 to the rafters. But “time heals” — Ainge later relented, and Rondo was among those who endorsed the C’s retiring Allen’s number.

Still, when asked about Allen’s retirement at the start of this season, Rondo was his usual icy self: